In classical physics, nonlocality (action at a distance) is a direct influence of one object on another distant object, in violation of the principle of locality. In quantum physics and quantum field theories, the term nonlocal means that correlations cannot be described by any local hidden variable theory. Such a form of non-locality does not allow superluminal communication. Many states which possess entanglement produce such correlations when measured, as demonstrated by Bell's theorem. This has been verified experimentally implying the absence of local hidden variables underlying quantum mechanics. In a recent publication it was found that quantum mechanics cannot be more non-local without violating the Heisenberg uncertainty principle. (wikipedia)